1. Field of the Invention
The present invention relates to a drive wheel equipped with a power spring in the drive wheel, and more particularly it relates to the structure of a drive wheel as above in which the number of elements and the number of manufacturing processes are reduced and mechanical loss is minimized.
2. Prior Art
A drive wheel having therein a flat spiral spring for giving power to the drive wheel according to the prior art is shown in FIGS. 3 and 4. In the figures, numeral 1 represents a casing or wheel frame of a drive wheel. The casing 1 comprises inner and outer side frames 1-1 and 1-2 made of synthetic resin or the like. The inner and outer side frames 1-1 and 1-2 are coupled to form a cylindrical hollow casing 1. The outer side frame 1-2 is formed with a drum housing 3 for accommodating a power spring 2. The inner side frame 1-1, which is mounted covering the outer side frame 1-2, is formed with a raised rim 4. A tire 5 made of rubber or the like is coupled about the casing 1 by means of the raised rim 4. Numeral 6 represents a partition wall fixedly mounted on one side of the drum housing 3. Recesses for bearing the shafts of gears housed within the casing 1 are formed in the partition wall 6 and the inner side frame 1-1.
A central or sun gear 25 is fixedly connected to a shaft 26 which is rotatably mounted centrally of the casing 1. The sun gear 25 is formed with an engaging section 24 to which one end of the power spring 2 in the drum housing 3 is fixed, the other end of the power spring 3 being fixed to the inner periphery of the drum housing 3. A fixed pinion 28 is fixedly connected to a chassis 1-3 of a vehicle (not shown) by means of an indentation section 27 formed on the surface of the fixed pinion 28. The shaft 26 of the sun gear 25 is rotatably inserted in the fixed pinion 28.
In cooperative association with the central gear 25 and the fixed pinion 28, there are provided with a spring winding gear train and a spring release gear train. The spring winding gear train comprises a shift gear 30 with its shaft 30' and a planetary gear 29 with its shaft 29', the shift gear 30 being movable generally concentrically of the rotation of the shaft 26 along an elongated slit 30-1. The spring release gear train comprises a shift gear 31 with its shaft 31', a spur gear 32 integrally coupled to the shift gear 31, and a planetary gear 33 with its shaft 33', the shift gear 31 being movable generally concentrically of the shaft 26 along an elongated slit 31-1. Both shift gears 30 and 31 are respectively provided with restoration springs 34 and 35.
With the drive wheel constructed as above, by pulling back a toy vehicle to which the drive wheel is mounted with the fixed pinion 28 connected to the chassis 1-3 via the indentation section 27, the casing 1 is rotated clockwise due to the friction between the tire 5 and the ground or floor. Upon rotating of the casing 1, the power spring 2 is wound up through the planetary gear 29 and the shift gear 30 of the spring winding gear train. On the other hand, after the power spring 2 is wound up, if the hand is released from the vehicle, then the sun gear 25 is rotated counter clockwise due to the release of the wound power spring 2. Thus, the toy vehicle runs forward by the power transmitted from the power spring 2, the planetary gear 33, the shift gear 31, and the spur gear 32 of the spring release gear train, and the fixed pinion 28.
In winding the power spring through the spring winding gear train, the shift gear 31 of the spring release gear train is returned to a restoration position by the spring 35. On the other hand, in driving the toy vehicle through the spring release gear train, the shift gear 30 of the spring winding gear train is returned to a restoration position by the spring 34. Therefore, in winding the power spring or driving the vehicle, both gear trains operate without interfering the operation of the other gear train.
The above mechanism however is associated with some problems. In particular, although the influences of centrifugal force during the rotation of the casing 1 are avoided because of the concentrical movement of the shift gears 30 and 31 relative to the rotation of the shaft 26, it is necessary to provide the respective restoration springs 34 and 35. Power transmission is carried out against the restoration springs 34 and 35 for the respective shift gears 30 and 31. Thus, fine adjustment of the spring force is difficult to obtain and mechanical loss in power transmission occurs due to the force acting against the spring force. Particularly, the larger the number of elements constituting the power transmission mechanism becomes, the more the proper mounting of the springs 34 and 35 becomes difficult. Furthermore, the number of assembling processes becomes large, thereby resulting in high manufacturing cost.